Conventionally, a navigation device that places a cross cursor on a guidance route on a map displayed on the screen of a display unit according to a user's command to enable the user to specify a scroll direction by using, for example, either one of four direction keys of a remote controller (abbreviated as a “remote control” from here on) to scroll the map along the guidance route (referred to as “along-route scroll” from here on) is known. For example, patent reference 1 discloses a navigation device that can efficiently display a point which is a target on a map through a brief operation, thereby being able to improve the operativity of the navigation device.
This navigation device has a first scroll mode in which, when an arbitrary point on a map image displayed on the display screen of a display is touched, the navigation device performs a one-touch scroll operation of placing a cursor at the point touched and scrolling the map image in such a way that the point is positioned at the center of the screen, and an 8-direction scroll operation of scrolling the map image on the display screen toward a direction shown by an arrow key pushed down, and a second scroll mode in which when the navigation device is providing route guidance, the navigation device performs a simulation scroll operation of scrolling the map image along the route being provided for the user, otherwise scrolling the map image along the road along which the vehicle is travelling to perform a learning scroll operation of storing the route.
Furthermore, patent reference 2 discloses a navigation device that, when a user checks a guidance route, scrolls a map along the guidance route automatically even if the user does not perform a scroll operation of scrolling the map along the shape of the guidance route. This navigation device sets a desired point as a destination and searches for a guidance route leading to this destination, and also scrolls and displays a map image according to movements of the position of a cursor. The navigation device is provided with a commanding means for issuing a command to move the cursor position, a determining means for determining whether the cursor position has moved to the vicinity of the guidance route according to the cursor position movement command issued by the above-mentioned commanding means, and a scroll control means for, when this determining means determines that the cursor position has moved to the vicinity of the guidance route, carrying out scroll control along this guidance route, and reducing the scroll rate as the cursor gets close to an intersection on this guidance route.    [Patent reference 1] JP,2006-214980,A    [Patent reference 2] JP,2002-22470,A
However, the conventional navigation devices which can carry out a scroll operation of scrolling a map along the route have the following problems. That is, in conventional along-route scrolling, when a cross cursor is placed at a slightly-curved portion of the guidance route, because directions along which the along-route scrolling can be carried out can be shown by highlighting two corresponding line segments of the cross cursor, the user is enabled to perform an along-route scroll operation of scrolling a map along either of the two directions: the direction of the destination and the direction of the place of departure by specifying one of the directions shown by direction keys. In contrast with this, when the cross cursor is placed at an acutely-curved portion of the guidance route, only one highlighted line segment of the cross cursor indicates the direction along which the along-route scrolling operation can be carried out because the direction of the destination and the direction of the place of departure which can be shown by the cross cursor get closer to each other. As a result, a problem is that only one direction can be shown by using the direction keys of the cross cursor, and the along-route scroll operation can be carried out only along the direction of the destination.
Furthermore, according to an existing along-route scroll method, when the user manually stops the scrolling of a map in the vicinity of the guidance route while operating the map scrolling, the navigation device makes a transition to an operation mode of along-route scroll (referred to as an “along-route scroll mode” from here on) because the cross cursor overlaps the guidance route. Because this transition is not necessarily an operation which the user desires, this causes a problem as a non-intended operation.
Furthermore, according to an existing along-route scroll method, when releasing the along-route scroll mode, the user is allowed to push down a direction key other than the direction keys respectively used for scrolling the map toward the direction of the destination and the direction of the place of departure to make the cross cursor leave the guidance route. A problem is however that because a direction key is typically used for moving a cursor in a menu or scrolling a map during a navigation operation, but is rarely used to break away from or release a certain function, it is hard for some users to understand how to release the along-route scroll mode.
In addition, according to an existing along-route scroll method, the user can know whether or not the navigation device is placed in the along-route scroll mode only from a change in the display form of the cross cursor, such as a change of the color of the cross cursor or highlighting of a line segment of the cross cursor with thickening of the line segment. A problem is therefore that it is hard for some users to understand whether or not the navigation device is placed in the along-route scroll mode only from a change in the display form of the cross cursor.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a navigation device that can carry out an along-route scroll operation in either of both directions, such as the direction of the destination and the direction of the place of departure, regardless of the shape of the guidance route, and that provides excellent user-friendliness.